Abstract: A method and apparatus for producing a high-velocity particle stream at low cost through multi-staged acceleration using different media in each stage, the particles are accelerated to a subsonic velocity (with respect to the velocity of sound in air) using one or more jets of gas at low cost, then further accelerated to a higher velocity using jets of water. Additionally, to enhance particle acceleration, a vortex motion is created, and the particles introduced into the fluid having vortex motion, thereby enhancing the delivery of particles to the target.

Abstract: The invention describes a method and apparatus for peening objects by means of ultrahigh velocity waterjet. The apparatus includes means for holding and producing relative motion in three dimensions of both the workpiece and the jet. Control means are provided to allow uniform and variable depth peening of complex shapes and automatic variations in relative speed, standoff distance, angle and pressure. The method includes the use of entrained disappearing particles in the waterjet to facilitate peening.